Synchronized stereocontrol of planar chirality by crystallization-induced asymmetric transformation
作者:Nobuhiro Kanomata、Gou Mishima、Jun Onozato
DOI:10.1016/j.tetlet.2008.11.021
日期:2009.1
Synchronized stereocontrol of two planar-chiral units was accomplished by using crystallization-induced asymmetric transformation (CIAT) of cyclophane-type bridged bisnicotinate derivatives 5b and 7. After screening various linkers, (S)-2-amino-1-butanol and (S)-tert-leucinol were found to be the most effective for CIAT of the corresponding bridged bisnicotinate 5b and 7, respectively, whose diastereomeric
A facile and practical removal of 2-oxazolidinone and 2-hydroxyethylamine auxiliaries was accomplished by treating the corresponding N-acyl-2-oxazolidin one and N-(2-hydroxyethyl)amide derivatives in simple methoxide-carbonate systems. The presence of excess DMC (dimethyl carbonate) accelerates the N-acyl bond cleavage for those substrates under mild reaction conditions, and the present method was found to be useful especially for the synthesis of planar-chiral nicotinate. (C) 2003 Elsevier Science Ltd. All rights reserved.
Adsorption-induced asymmetric transformation of planar-chiral pyridinophanes
作者:Nobuhiro Kanomata、Jun Oikawa
DOI:10.1016/s0040-4039(03)00699-3
日期:2003.4
Stereocontrol of cyclophane-type planar chirality was investigated via adsorption-induced asymmetric transformation (AIAT) on a series of inorganic porous adsorbents. The rope-skipping equilibria between bridged nicotinamides (S,3'S)-1 and (R,3'S)-2 shifted preferentially to (R,3'S)-2 to accumulate (R)-configuration of planar chirality with up to 61% de (ca. 4/1 ratio) on alumina. The results are in good contrast to accumulation of the corresponding (S)-configuration via conventional crystallization-induced asymmetric transformation (CIAT) to the solid (S,3'S)-1a-d. (C) 2003 Elsevier Science Ltd. All rights reserved.